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Future steel

Fabian Schmidt / cbNovember 19, 2014

A new casting process has made it possible to create stronger and thinner steel alloys than before. It's thanks to collaboration between academia and industry. The team is up for the German Future Prize.

https://p.dw.com/p/1DoYm
Man fills steel into a horizontal casting plant at Salzgitter AG in Peine (Photo: Ansgar Pudenz / German Future Prize)
Image: Ansgar Pudenz

The demands on steel get greater by the day: steel needs to be soft enough to shape - for car body parts, for example - but strong and solid, and as thin and light as possible.

You would think such demands were mutually exclusive.

But in the northern German city of Peine, there's a steel works which plans to deliver alloys of this kind very soon.

The developers - from academia and industry - have been nominated for the "Deutscher Zukunftspreis", or #link:http://www.deutscher-zukunftspreis.de/en:German Future Prize#.

One steel - multiple levels

A role with finished hot-rolled steel from a hot rolling mill of Salzgitter AG (Photo: Ansgar Pudenz / German Future Prize).
New steels need to hold 'mutually exlusive' propertiesImage: Ansgar Pudenz

One of their alloys is called High Strength and Ductility, or HSD steel. It contains a lot of manganese, and can be stretched, but is also extremely tough.

It could be very useful in the production of cars. With HSD steel, car bodies could be a lot lighter, because the steel sheets would be thinner than they are now, but remain just as stable.

But there's a catch: HSD steel can only be made with Belt Casting Technology (BCT) which was developed by Siemag AG in Dusseldorf. And there's only one factory using BCT. It's a completely new process.

"We cast steel horizontally," engineer Jochen Wans, director of technical distribution at Siemag, said at the Steel Conference in Dusseldorf on November 6."That means there's no strain on the product."

The casting process, says Wans, is free of any tension, pull or pressure. "That's how we guide the casting product through the machine and solidify it."

Less tension

Steel is usually cast vertically in slabs. These are metal blocks, which are at least 15 centimeters thick and several meters long. The slabs are then steamrollered into sheets.

But this process has two disadvantages: first, the slabs are moved from a vertical to a horizontal position during the casting process - that is, they are still half-fluid and are bent for a short time before being straightened again. This leads to tension inside the steel, which affects the quality of the finished product.

And second, it takes a lot of steamrollering to get thin sheets from the thick slabs.

Nominated fort he German Future Prize: Ulrich Grethe (SMS-Siemag), Burkhard Dahmen (Salzgitter) und Prof. Karl-Heinz Spitzer (Universität Clausthal) (Foto: Ansgar Pudenz/ Deutscher Zukunftspreis).
Ulrich Grethe (SMS Demag), Burkhard Dahmen (Salzgitter) and Karl-Heinz Spitzer (Clausthal University of Technology)Image: Ansger Pudenz/Deutscher Zukunftspreis

The new casting process doesn't have such issues. Nothing needs to be tilted and the slabs are only 1.5 centimeters thick to begin with. That puts less stress on the material during warm rolling - which is ideal for alloys like HSD steel.

Clean surfaces

The new set-up has another advantage: the casting takes place in a vacuum. The casting room is filled with the noble gas, argon. It stops the steel from oxidizing, giving it a higher quality surface.

The finished casts' first contact with air is when they are cooled and solid. There is also no contact with water during the cooling process. This way, the inside texture of the steel can form very evenly.

However, the sheets still need to be steamrollered.

Close to industrial production

The belt casting factory has been in trial mode since the end of 2012. It's equipped for an annual production of 40,000 tons of steel.

Finished steel plate of the new strip casting method (Photo: Ansgar Pudenz / German Future Prize)
The moulded steel plates are only 0.5 inches thickImage: Ansger Pudenz/Deutscher Zukunftspreis

In the early days of the factory, they produced regular construction steel. Since February 2014, Salzgitter AG has also been testing production of the more demanding, HSD steel.

Optimistic outlook

After the first nine months, Salzgitter AG engineer Peter Juchmann says he is happy with the results.

"The general process of belt casting has shown a positive robustness and acceptable reliability," Juchmann says.

But there is room for improvement.

"The quality of the HSD products isn't high enough to lead to a satisfactory warm rolling result," he says.

So it may be a while before the first HSD steel products hit the market. But they are confident they will get there.

Successful cooperation

All this would not have been possible without a close cooperation with researchers at the Clausthal University of Technology. Professor Karl-Heinz Spitzer ran preparations at a small trial facility.

"The facility in Clausthal was run as a pilot factory," says Jochen Schlüter, who studied metallurgy at Clausthal and is now in special developments at Siemag. "They did many analyses there that were the basis for us to convert the project to an industrial scale. That's not only a big factor in this project's success, but in all of Germany's - the close connection between universities and industry."